DOCBOOK: table question

[Jeff Rancier <jeff.rancier@softechnics.com>]

Should I be able to have a <entrytbl/> in place of an <entry/> in a <row/>?
The following doesn't work.  I have the following format for a table:

    <table frame="all">
      <title></title>
      <tgroup cols="4" align="left" colsep="1" rowsep="1">

        <thead>
          <row>
            <entry></entry>
            <entry></entry>
            <entry></entry>
            <entry></entry>
          </row>
        </thead>

        <tbody>

          <row valign="bottom">
            <entry></entry>
            <entry></entry>
            <entry></entry>
            <entry></entry>
          </row>

          <row>
            <entry></entry>
            <entry></entry>
            <entry></entry>
            <entrytbl cols="2">
              <tbody>
                <row>
                  <entry></entry>
                  <entry></entry>
                </row>
              </tbody>
            </entrytbl>
          </row>

        </tbody>
      </tgroup>
    </table>

Thanks.
Jeff